Tantalum Interconnect Metallization for Thin-Film Neural Interface Devices

Area of Science:

• Materials Science
• Neuroscience
• Electrical Engineering

Background:

• Neural interfaces utilize conductive metal traces for electrical interconnects, traditionally relying on noble metals.
• Tantalum (Ta) has potential as an alternative interconnect metallization for neural devices, but its properties require further characterization.

Purpose of the Study:

• To investigate tantalum (Ta) as a replacement for noble metal interconnects in thin-film neural interfaces.
• To characterize the structural and electrical properties of sputter-deposited tantalum on amorphous silicon carbide (a-SiC).

Main Methods:

• Tantalum was deposited onto a-SiC with and without a titanium (Ti) adhesion layer using sputtering.
• Resistivity, crystal structure (X-ray diffraction), and feature size fabrication (photolithography, RIE) were analyzed.
• Microelectrode arrays with α-Ta and gold (Au) interconnects were tested using cyclic voltammetry and current pulsing.

Main Results:

• Tantalum's resistivity varied significantly based on the presence of a Ti adhesion layer, with α-Ta (on Ti) showing low resistivity (35 ± 6 µΩ·cm) and β-Ta (direct deposition) showing high resistivity (197 ± 31 µΩ·cm).
• Fabricated microelectrode arrays demonstrated stability over 500 cyclic voltammetry cycles.
• α-Ta interconnects exhibited a small increase in access voltage (21 mV) compared to Au under current pulsing.

Conclusions:

• Tantalum, particularly the α-Ta phase, is a promising low-resistivity material for thin-film metallization in neural interfaces.
• Tantalum interconnects demonstrate good stability and comparable performance to gold, warranting further investigation for neural device applications.